In general, a manifold block of a fuel cell stack is a common distributor, which mounted to a portion of the stack, has passages therein for supply or discharge of hydrogen and air for generating electricity in the stack. Such a manifold block is equipped with a hydrogen supply system, which includes a hydrogen cutoff valve, a hydrogen supply valve, a hydrogen purge valve, a water trap and drain valve, and a hydrogen ejector, for optimizing the performance and the packaged structure of the fuel cell system. Hydrogen passages, through which hydrogen flows, are formed in the hydrogen supply system and the manifold block.
The manifold block has a highly complicated structure in order to provide passages for ensuring the smooth movement of hydrogen in the limited space in the manifold block. Currently, the manifold block is manufactured using an aluminum gravity casting method.
However, because aluminum ions are eluted from the aluminum and the eluted aluminum ions deteriorate the performance of a membrane-electrode assembly, which is a main component of the stack, a surface-coating process must be performed on the passages in the manifold block in order to prevent the elution of aluminum ions.
Further, the surface-coating is time-consuming because the passages in the manifold block are complicated, post-processing must be performed after the casting of the manifold block, and it takes a lot of time to process the manifold block because various components mate with corresponding portions of the manifold block.
Furthermore, the manifold block made of an aluminum material lowers the temperature of the air introduced into the stack during the cold-start operation of the stack, thus having a bad influence on the cold-start operation.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention, and therefore, it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.